/Engine/Plugins/Experimental/Mutable/Source/CustomizableObject/Classes/MuCO/CustomizableObject.h
Call after having used Mutable's Projector testing with mask out features. It should be unloaded because it can spend quite a lot of memory.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category=CustomizableObject) void UnloadMaskOutCache()